Limit stop for cranes or hoists



C. J. GARRIGAN LIMIT STOP FOR CRANES 0R HOISTS Sept. 15, 1925.

Filed Jan-Q l2, 1923 INVENT v I I a Patented Sept. 15, 1925.

PATENT OFFICE.

CORNELIUS J'. GARRIGAN, OF MILLVALE, PENNSYLVANIA.

LIMIT STOP FOR GRANES OR HOISTS.

Application filed January 12, 1923. Serial No. 612,223.

To all whom it may concern:

Be it known that I, CORNELIUS J. GABRI- GAN, a citizen of the United States, and resident of Millvale, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Limit Stops for Cranesor Hoists; and I do hereby declare the following to be a full, clear, and exact description thereof.

My invention relates toa limit stop for cranes, hoists or other devices driven by direct current electric motors where the travel of same is limited.

Many serious and often times fatal accidents occur in factories due to the overtravel of electrically driven machinery, more particularly the over-travel of the hookblocks of electric cranes. The object of my invention is to provide a limit stop which is sure and positive in operation, and which can be depended on under all conditions to operate effectively to prevent the over-travel of the hook-blocks of electric cranes, and so eliminate the danger due to such over-travel.

In the accompanying drawing, Fig. 1 is a side elevation of my improved limit-stop showing in full lines the position of the parts when the stop is closed by the hookblock in the hoisting direction; Fig. 2 is a front elevation of same; and Fig. 3 is a plan view.

In the drawing is shown a suitable frame made up of the four uprights 3 which are secured by screws 4 to the upper wooden block 5.

This frame is suspended by the chains 6 from any suitable overhead support.

U-shaped guides 7 pass through the block and are held in place by nuts 8.

A suitable electrical contact 9 is secured to the block 5.

Secured to opposite sides of the block 5 by the bolts 10 are the inclined arms 11. The outer ends of the arms 11 ar pivotally connected as at 12 to the arms 13 which are secured by the bolts 14 to the lower wooden block 15 which carries the contact 16.

The arms 11 and 13 are connected by the chains 17 which limit the downward movement of the arms 13, and consequently the lower block 15.

U-shaped guides 18 are connected by the nuts 19 to the block 15, and said guides,

guides for thepassage of the hoist-cable 20 to which is clamped the stop-block 21.

The contacts 9 and 16 are connected in series in the motor armature circuit on one side, and to the field circuit on the other side. This system of connections gives assurance that the limit stop is in operating position at all times so long as the motor circuit is intact. 7

When my improved limit stop is in use, the hoist cable'20 travels up through the guides 7 and 18, the stop-block 21 comes in contact with the lowermost guide 18, and said guide is moved upwardly, carrying with it the block 15 until the parts assume the position of the full lines, Fig. 1, which brings the contacts 16 and 9 into contact, thereby shzort-circuiting the armature and increasing th amount of current passing through the field, thereby bringing the hoist motor to stop quickly. By simply reversing the controller to operate in the lowering direction, the armature short-circuit through the limit stop is made inoperative and the stop-block may be lowered automatically, opening the limit stop and restoring same to normal position.

The device is absolutely, positive in operation, and 'due to its simplicity there is nothing to getout of order, for the hoist cable cannot move upwardly to stopping position without bringing the stop block 21 into engagement with the guides 18 to bring the contacts into contact.

It is of course apparent that instead of using the special stop-block 21 the ordinary sheave-block on the cable 20 may be employed to lift the arms 18 to make the contact.

What I claim is:

A limit stop for cranes and the like com prising a pair of electric contact blocks normally vertically spaced and flexibly sup ported from a point thereabove, and vertically spaced guides for said blocks adapted to receive a hoist cable, the guides on the lower block being adapted to be engaged by a stop member on the hoist cable.

In testimony whereof I, the said Con- NELIUS J. GARRIGAN, have hereunto set my hand.

CORNELIUS J. GARRIGAN. 

